Sur d’autres sites (14347)

• mmaldec : limit internal buffering

  14 avril 2016, par wm4

  mmaldec : limit internal buffering
  This uses a new MMAL feature, which limits the number of extra frames
  
  that can be buffered within the decoder. VIDEO_MAX_NUM_CALLBACKS can
  
  be defined as positive or negative number. Positive numbers are
  
  absolute, and can lead to deadlocks if the user underestimates the
  
  number of required buffers. Negative numbers specify the number of extra
  
  buffers, e.g. -1 means no extra buffer, (-1-N) means N extra buffers.
  Set a gratuitous default of -11 (N=10). This is much lower than the
  
  firmware default, which appears to be 96.
  This is backwards compatible, but needs a symbol only present in newer
  
  firmware headers. (It’s an enum item, so it requires a check in
  
  configure.)
  Signed-off-by : Anton Khirnov <anton@khirnov.net>
  

  • [DBH] configure
  • [DBH] libavcodec/mmaldec.c

• How can I limit the file size when doing a write() while writing data from a video stream in Python

  8 avril 2016, par Michael Bailey

  I am pulling in a video stream of an unknown length and writing that file to disc using .write() in Python. My basic need is to have a rolling 2-3 minutes of video recorded to that file at all times VS having that file grow to a huge size. On the other end I’m using FFMPEG to grab clips from the .dat file being written.

  with open("./site/files/tmp/" + hashid + ".dat", 'wb') as f:
  
          while True:
  
              data = stream.read(1024)
  
              f.write(data)

  Alternately if you know a way I could store that same data in memory probably only 20-50mb (2-3 mins) and send that to FFMPEG that might be an even better option as well. I’m calling FFMPEG via Popen subprocess.

• FFmpeg command to apply multiple filters and limit the final file size

  16 mars 2016, par Konrad — ffmpeg

  I’m using ffmpeg command below to convert video to a format of the defined scale and in order to hardcode the subtitles

  Original syntax

  ffmpeg -i "Original File.mov"  -vf subtitles=Subtitles.srt -vf scale=1920:1080 \
  
         -crf 12 "Final File".mov

  Problem

  I would like to expand this command further and :

  • ensure that the produce file is under 2GB
  • I would like to include additional parameters with advanced subtitle options, like setting the canvas size and fixing the potential delay

  Side notes

  I reckon that in case of predefining the file size the -crf 12 paramater will be redundant ?